REDUCING DRY SKIMS (MZR, NIFTY, BETTER FLUX)
A galvanizer had a third-party test his flux monthly, and the results were wrong: The reported sulfate and iron were only half reality; the pH was reported as 4.6, but was actually above 6. The galvanizer was having numerous "black" (bare) spots. 50 mL of this flux was titrated with 1:10 dilute HCl to the bromophenol blue end-point and calculation showed that 50 gallons of conc. HCl was required to attain pH = 4.2. Ammonium chloride was added to raise the ACNV. All black spots stopped instantly.
After adding the HCl and ammonium chloride, parameters for this bad flux were: Baumé = 19.5; pH = 4.2; ACNV = 1.0; SO4-2 = 1.4%; Fe+2 = 0.6%; 160F; Total NTNV's = 3,725 ppm (CaCl2 = 1,277 ppm; MgCl2 = 245 ppm; MnCl2 = 250 ppm; KCl = 338 ppm; NaCl = 1,615 ppm).
This company galvanizes 200,000 pounds/day of 1/8 inch thick structural steel and using the above bad flux produced 4,000 pounds of unworked dry skims/day. Using an MZR machine to recover metallic zinc the yield was 60%. With no other changes --we installed NiftyGalv in this plant and the MZR yield (recovery of usable zinc) increased from 60% to 78%. At $1.30/lb for zinc and $0.30/lb for skims. NiftyGalv is a $180,000/year benefit to this galvanizer.
For the same plant, a decision was made to make the flux better. We took out half the flux tank and put it down a deep-well so as to reduce the impurities and decrease the baumé. Ammonium chloride was added to increase the ACNV. The resulting better flux has the following parameters: Baumé = 12.0; pH = 4.2; ACNV = 1.6; SO4-2 = 0.7%; Fe+2 = 0.3%; 160F; Total NTNV's = 1,900 ppm.
Amazingly, the unworked dry skims reduced from 4,000 lb/day to 1,000 lb/day by using this better flux. Also the MZR metallic zinc yield improved from 78% to 80%. Calculation for % (final ash/production) times 100% is: 1,000 lb ash/day times 250 days times 20% = 50,000 lbs ash/year. Thus % ash to production = (50,000 lbs ash/50,000,000 lbs production) times 100% = 0.10%, which is a very, very low number. Some NiftyGalv clients are getting an 85% yield from the MZR machine. With NiftyGalv the inside of the MZR barrel is much cleaner. Workers report almost no kettle zinc spatter, much less kettle smoke, virtually no black spots, much less zinc clean-up, and excellent quality. By using NiftyGalv and better flux this galvanizer has increased production to over 300,000 pounds/day and set a new record of 462,000 pounds in 11 hours with 13 workers. To further increase production, acid pickling must be faster, and zinc thermal capacity must increase.
Prior to NiftyGalv and better flux the %GZU was 6.2% and is now 5.2%. Based on 50,000,000 pounds production/year and $1.30/lb zinc this is a total $650,000 of zinc that this galvanizer will not purchase.
NOTES: European and North American galvanizers do not use the same flux formulation or fluxing methods and therefore the above experience may not apply in Europe. By using NiftyGalv and secondary MZR zinc galvanizing quality is consistently excellent.
PYROTEK did not take part in this work.
NiftyGalv---- Dr. Thomas H. Cook 1 605 745 4567 *
27793 Cheyenne River Road
Hot Springs, South Dakota USA 57747
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